Detecting mains current

Hi there,

I'd like to know if there's an easy and preferably cheap (in terms of components) way that my PIC can determine whether current is being drawn by a mains level (i.e. 240V) device. Ideally it would be nice to know how much current too.

There's nothing to stop me wiring this device into the mains cable, but obviously the pic operates on 5v, and I don't know how to connect the two without incinerating the pic.

I'm sorry if this is a really inane questions - while I'm reasonably happy with the programming side of things my knowledge of electronics is fairly elementary.

Any suggestions are appreciated.

Thanks.

With a current transformer you can see if there is a current flowing.
It's is also possible to take an lowohmic power resistor and a rectifier bridge together connected to an optocoupler. When a sertain vallue of current is flowing the led in the optocoupler is lit and the transistor at the other end is conducting.
Take in this case an optocoupler what is made for mainsvoltages.

http://www.allegromicro.com/hall/currentsensor.asp

Hi,
You can use a hall effect sensor for that. If you want to measure the current have a look at Allegro they have a line of sensors that may be what you are looking for.

http://www.allegromicro.com/hall/

IIRC there have been some previous discussions about this, do a little searching on the forum and see if turns up something.

/Henrik Olsson.